Treatment of tobacco and tobacco smoke with chelating agents to remove Pb-210 and Po-210

ABSTRACT

This invention relates to the treatment of tobacco and tobacco smoke with chelating agents to reduce the concentration of Pb-210 and Po-210. Chelating formulations such as the tetrasodium salt of ethylenediaminetetraacetic acid in aqueous solution with a wetting agent are sprayed onto the tobacco during growth and/or the chelating formulations are used to soak or wash the tobacco after harvest but before curing the tobacco. Pb-210, Po-210 and other metals are removed from tobacco smoke by applying chelating agents to the surface of the tobacco and/or the filter material.

BACKGROUND

This invention relates to methods of treating tobacco to reduce the Pb-210 and Po-210 content of tobacco and tobacco smoke. The invention describes the material used to treat the tobacco and tobacco smoke and the methods of treatment.

The National Council of Radiation Protection and several scientific papers report that Pb-210 and Po-210 have been detected in tobacco and cigarette smoke. The literature also indicates increased concentration of these radionuclides in the lungs, skeletons and other body tissues of smokers when compared to non-smokers. Furthermore, the Po-210 has been reported to concentrate at the bifurcation of segmental bronchi in the lungs of smokers which can result in a relatively high localized radiation dose. It is highly probable that the Pb-210 and Po-210 deposited in the lungs along with other materials in smoke contribute to the induction of lung cancer. Radon studies indicate that a synergism exists between smoking and the radiation dose to the lung from radon daughters resulting in lung cancer. Since the Pb-210 and Po-210 in tobacco smoke will most likely be deposited at the same locations and in conjunction with other chemicals in smoke, a synergism between the Pb-210 and Po-210 and other chemicals in tobacco smoke is also expected. It is therefore possible that the reduction of Pb-210 and Po-210 concentrations in tobacco, tobacco smoke and tobacco products would have the effect of reducing lung cancer caused by smoking. There is evidence that smokers have a higher incidence of cancers other than lung cancer. Tobacco smoke has been shown to cause approximately 22 percent of all cases of myeloid leukemia making it the leading known cause of this disease. Furthermore, the Pb-210 and Po-210 in the smoke have been identified as the most probable cause of this cancer resulting from smoking. The Pb-210 and Po-210 inhaled with smoke that is cleared from the lung is efficiently transferred from the gastrointestinal tract to bone tissue where it has a long residence time of over ten years. The concentrations of Pb-210 and Po-210 in the skeleton of smokers have been measured at 2 to 3 times higher than the concentration in nonsmokers. Most of the Pb-210 and Po-210 in non-smoker smokers results from Pb-210 and Po-210 in food. Reducing the Pb-210 and Po-210 in tobacco and tobacco smoke will reduce the body burden of Pb-210 and Po-210 in the skeleton and other tissues of the body resulting from the inhalation of smoke and most probably will reduce the incidence of lung and other cancers. In an article in Science, “Toward the Primary Prevention of Cancer,” Vol. 254, p. 1131 (1991), the authors point out that, “Ominously, in many populous developing countries current tobacco consumption has surpassed even the highest levels achieved in the United States, and the eventual toll in the morbidity in these countries will be staggering.” The authors believe that it is imperative for researchers to explore measures to make smoking safer. The processes described in this invention can result in a substantial reduction in the radiation dose to men and women at very little cost.

The Pb-210 and Po-210 in tobacco results primarily from the deposition of airborne radon decay products on the leaves of the tobacco plant during its growth. Tobacco leaves have characteristics that retain the radon decay products when they deposit on the leaves. The uptake of Pb-210 and Po-210 via the root system does not appear to contribute significantly to the Pb-210 and Po-210 in tobacco.

Various chelating agents are often added to food products to bind with the metals that may be present in the food to retard decay and discoloration and to enhance flavor. It has also been suggested that chelating compounds, in addition to other chemicals, be added to tobacco and tobacco products to enhance the flavor of the tobacco (U.S. Pat. No. 3,988,487 October 1976 Sanderson et al). In these processes, the chelating agent is added to the tobacco and/or food where it may bind with metals including Pb and Po. However, the Pb and Po remain with the tobacco and food and will be inhaled or ingested.

In the paper, “polonium-210: A Questionable Risk Factor in Smoking-Related Carcinogenesis,” by Naomi H. Harley, Beverly S. Cohen and T. C. Tso, Banbury Report, A Safe Cigarette? Edited by G. B. Gori and F. G. Bock, Cold Spring Harbor Laboratory (1980), the authors reported some work on the removal of radioelements with chelating agents. The removal of Po-210 using a chelating agent was conducted on cured tobacco leaf and on homogenized leaf curing-processed material. The work was done in collaboration with W. Selke's laboratory (Research Department, Schweitzer Divison, Kimberly-Clark Corporation). The removal process reduced the Po-210 level in cured leaf from 0.22 (control) to 0.05 pCi (chelated). For the homogenized leaf curing material, the Po-210 was reduced from 0.13 (control) to 0.06 pCi (chelated). To our knowledge, all tests used cured tobacco.

In a paper by Erich W. Bretthauer and Stuart C. Black, “Polonium-210: Removal from Smoke by Resin Filters,” Science, Vol. 156, pp. 1375-6 (1967), the authors used a 20 to 50 mesh mixture (1:1) cation and anion exchange resin intended for water-demineralization cartridges in the filter of cigarettes to remove Polonium-210 in the mainstream smoke. In their tests, they used cigarettes with filters consisting of a chamber containing granular charcoal, with rolled-cellulose elements before and after the charcoal chamber. To test the effectiveness of the ion exchange resin in removing Po-210, they used cigarettes with the charcoal cellulose filters unchanged and cigarettes with the granular charcoal removed and replaced with the 20 to 50 mesh ion exchange resin. The cigarettes with the granular charcoal removed about 50 percent of the Po-210 in mainstream smoke and the filter with the resin substituted for the charcoal removed 92 percent or more.

SUMMARY

The invention described in this application relates to the treatment of tobacco and tobacco smoke with chelating agents to remove Pb-210 and Po-210 and other metals. In the treatment of tobacco, chelating formulations such as the tetrasodium salt of ethylenediaminetetraacetic acid (Na₄EDTA) in aqueous solution with a wetting agent are sprayed onto the tobacco plants during growth and/or the chelating formulations are used to soak or wash the tobacco after harvest but before curing the tobacco. The chelating formulations are applied before curing to facilitate the removal of Pb-210 and P0-210. During curing the sticky exudates on the surface of the tobacco leaves hardens into a resinous material with most of the Pb-210 and Po-210 held within the hardened resin making removal more difficult. To remove the Pb-210, Po-210 and other metals from tobacco smoke, chelating agents such as Na₄EDTA are applied to the surface of the cured tobacco and/or to the surface of the material used in the filter. The Pb-210, Po-210 and other metals in the smoke can then react with the chelating agent on the unburned tobacco and/or with the chelating agent on the filter material to reduce the amount of Pb-210, Po-210 and other metals inhaled by the smoker.

DESCRIPTION OF THE INVENTION

Treatment of Tobacco with Chelating Agents

In the treatment of tobacco, the chelating agent is used in aqueous solution with or without wetting agents. The chelating formulation can be applied to the leaves of the plant during growth or after harvest but before curing. Treatment may involve spraying the leaves or soaking the leaves with or without mechanical agitation. In addition to reducing the Pb-210 and Po-210 content of the tobacco, the aforementioned treatment will have the added benefit of reducing the concentration of other metals such as cadmium, zinc, nickel, copper, thorium, uranium and non radioactive lead that are found in tobacco and tobacco smoke.

EXAMPLE 1

Within three hours after harvesting, tobacco leaves were immersed and gently agitated in an aqueous solution of 1% Na₄EDTA and a wetting agent for one minute. The wetting agent used was 0.5 ml. of a 10% aqueous solution of dioctyl sodium sulfosccinate per liter of chelating solution. The leaves were then rinsed for one minute in water and hung in bunches to dry and cure. A separate set of leaves, harvested at the same time, was hung in similar bunches to cure. Both sets of leaves were left hanging indoors for two weeks. There was no apparent difference in appearance, smell and texture of the treated and untreated leaves. The treated and untreated leaves were then shredded and separately placed in 500 ml. plastic bottles. The Pb-210 concentration was measured by gamma spectroscopy using a high purity germanium detector. The Pb-210 concentration for the untreated leaves was measured at 1.2 pCi/g and the Pb-210 concentration for the treated leaves was measured at 0.2 pCi/g, indicating that approximately 80% of the Pb-210 had been removed. Washing tobacco leaves with water alone had no effect in reducing the Pb-210 concentration. Increasing the concentration of chelating agent and/or the time the leaves are washed with the chelating formulation will result in more complete removal of the Pb-210 and the Po-210.

EXAMPLE 2

Cured tobacco leaves were soaked with gentle agitation in an aqueous solution of 1% Na₄EDTA and a wetting agent for one minute and then rinsed for one minute in water using the same wetting agent as in Example 1. Before treatment, the tobacco was measured at 1.4 pCi/g Pb-210 and after treatment the Pb-210 was measured at 0.8 pCi/g. It is estimated that about 40% of the Pb-210 was removed. Treating the tobacco with water (soaking and rinsing) had no effect in reducing the Pb-210 content.

Although the Po-210 was not measured in these experiments, it is expected that the chelating agents will be as effective in removing the Po-210 as they are for Pb-210. In addition, Pb-210 is the precursor for Po-210 so that once the Pb-210 is removed, Po-210 cannot be formed on the tobacco or in the human body from the decay of Pb-210. Tobacco is often aged for years prior to use. Since Po-210 has a half life of 138 days, most of the unsupported Po-210 would decay away during storage.

Although it has been previously demonstrated that chelating agents can be effective in removing the Pb-210 and Po-210 from cured tobacco, we believe there are advantages in treating tobacco during growth or shortly after harvest before the tobacco is cured. Most of the Pb-210 and Po-210 that is on the tobacco is trapped on the surface of the leaf by a sticky substance on the tricomes of the tobacco. If treated with chelating agents before curing, the Pb-210 and Po-210 are quite easily removed. After curing, the sticky exudates harden into resinous material with most of the Pb-210 and Po-210 held within the hardened resin. To remove the Pb-210 and Po-210 from cured tobacco using chelating agents requires higher concentrations of chelating agent and longer contact time than is needed in the treatment of tobacco before curing as is demonstrated in examples 1 and 2 above. In addition, treatment of tobacco before curing may have less effect on the removal of constituents that make smoking organoleptically acceptable.

Removing Pb-210 and Po-210 from Tobacco Smoke

A chelating agent or a combination of chelating agents can also be applied to the tobacco and/or filter material to reduce the Pb-210 and Po-210 in the smoke and combustion products passing through the tobacco and/or the filter material. When a chelating agent or a combination of chelating agents have been applied to tobacco, the volatilized and particle borne Pb-210 and Po-210 produced by the burning tobacco will react with chelating agents on the surface of the unburned tobacco removing Pb-210 and Po-210 from the smoke and combustion products being drawn through the unburned tobacco. Similarly, chelating agents applied to the surface of or incorporated into the filter material used in filtering tobacco smoke and combustion products will remove Pb-210 and Po-210 in the smoke and combustion productions passing through the filter material. The literature (Polonium-210: Removal From Smoke by Resin Filters by Erich W. Bretthauer and Stuart C. Black, Science, 156 (3780) pp. 1375-1376, 1967) indicates that the use of cation and anion exchange resins in the filters of cigarettes removed some of the Po-210 from the tobacco smoke passing through the filter. The resins used apparently have sulfate and trimethylamine functional groups to react with the Po-210. We believe chelating agents such as Na₄EDTA applied to the surface of the tobacco and/or filter material or otherwise incorporated into the filter will be more effective in removing Pb-210 and Po-210 from the smoke. Applying a chelating agent to the surface of the tobacco and/or filter or otherwise incorporating the chelating agent into the filter may facilitate advantages in production over the process described by Bretthauer and Black. In addition to Pb-210 and Po-210, tobacco smoke contains significant concentrations of other radioactive and non-radioactive metals that may be toxic when inhaled. Metals in tobacco smoke with the highest concentrations are zinc, lead, cadium and copper. The process described in the application to reduce the concentration of Pb-210 and Po-210 in tobacco smoke will also reduce the concentration of the other metals in the tobacco smoke. 

1. We claim the treatment of tobacco, before the tobacco is cured, with chelating agents such as triethanolamine, ethylenediaminetetraacetic acid, EDTA, the disodium salt, Na₂EDTA, the tetrasodium salt, Na₄EDTA, and the pentasodium salt, Na₅DPTA, to remove the Pb-210 and the Po-210, where the tobacco is washed by soaking or spraying with an aqueous solution of the chelating agent that may or may not include a wetting solution such as dioctyl sodium sulfoccinate and where the aqueous solution of the chelating agent may also include chemicals to control the pH of the solution and where after soaking or spraying the tobacco with the chelating solution, the tobacco may or may not be rinsed with water.
 2. We claim the process of removing Pb-210 and Po-210 from tobacco as in claim 1, where tobacco is treated after harvesting but before curing.
 3. We claim the process of removing Pb-210 and Po-210 from tobacco as in claim 1, where the tobacco treated is the tobacco plant before harvest where the chelating solution is sprayed onto the plants.
 4. We claim the treatment of smoke and combustion products of burning tobacco with chelating agents to remove Pb-210 and Po-210 and other metals, where the chelating agents that can be used include but are not limited to triethanolamine, ethylenediaminetetraacetic acid, EDTA, the disodium salt, Na₂EDTA, the tetrasodium salt, Na₄EDTA, and the pentasodium salt, Na₅DTPA.
 5. We claim the process of removing Pb-210, Po-210 and other metals from smoke and combustion products of burning tobacco as in claim 4, where a residue of one or more chelating agents are applied to the surface of the cured tobacco so that the volatized and particle borne Pb-210, Po-210 and other metals produced by the burning tobacco can react with chelating agents on the surface of the unburned tobacco removing Pb-210, Po-210 and other metals from the smoke and combustion products being drawn through the unburned tobacco.
 6. We claim the process of removing Pb-210, Po-210 and other metals from smoke and combustion products of burning tobacco as in claim 4, where one or more chelating agents are applied to the surface of filter materials or otherwise incorporated into the filter material, where the chelating agent or combination of agents on the surface of the filter material and/or made part of the filter material would serve to remove Pb-210, Po-210 and other metals from the tobacco smoke and combustion products drawn through the filter, where the filter may or may not be directly attached to the tobacco being smoked. 